There are lots of scammers out there and we need to be very careful especially when sending funds to other people, it's his/her mistake because he just send btc to someone he really don't know meaning he didn't do strict due diligence and there's now way he can recover it because transactions are irreversible.
The security system is always penetrated by hackers, with the aim of stealing crypto from penetrated accounts. So, e-wallet security must always be updated, because hackers can enter anywhere. For example, from a scam email or from the internet when browsing accidentally enters hackers' content.